
package org.apache.solr.request;

import org.apache.solr.common.util.NamedList;
import org.apache.solr.core.SolrInfoMBean;
import org.apache.solr.response.SolrQueryResponse;

/**
 * Implementations of
 * <code>SolrRequestHandler</code> are called to handle query requests.
 *
 * Different
 * <code>SolrRequestHandler</code>s are registered with the
 * <code>SolrCore</code>.
 * One way to register a SolrRequestHandler with the core is thorugh the
 * <code>solrconfig.xml</code> file.
 * <p>
 * Example
 * <code>solrconfig.xml</code> entry to register a
 * <code>SolrRequestHandler</code> implementation to
 * handle all queries with a Request Handler of "/test":
 * <p>
 * <code>
 *    &lt;requestHandler name="/test" class="solr.tst.TestRequestHandler" /&gt;
 * </code>
 * <p>
 * A single instance of any registered SolrRequestHandler is created
 * via the default constructor and is reused for all relevant queries.
 *
 *
 */
public interface SolrRequestHandler extends SolrInfoMBean {

    /**
     * init will be called just once, immediately after creation.
     * The args are user-level initialization parameters that
     * may be specified when declaring a request handler in
     * solrconfig.xml
     */
    public void init(NamedList args);

    /**
     * Handles a query request, this method must be thread safe.
     * <p>
     * Information about the request may be obtained from
     * <code>req</code> and
     * response information may be set using
     * <code>rsp</code>.
     * <p>
     * There are no mandatory actions that handleRequest must perform.
     * An empty handleRequest implementation would fulfill
     * all interface obligations.
     */
    public void handleRequest(SolrQueryRequest req, SolrQueryResponse rsp);
}
